An automotive vehicle conventionally utilizes a hollow, tubular drive or propeller shaft for transmitting driving torque from the engine to the driving wheels. It is not uncommon for such shaft to be subjected to vibrations from one or more sources. It is desirable to damp such vibrations so as to provide for a quieter and smoother ride.
Most of the propeller shafts in use heretofore have been of uniform diameter from one end to the other. Recently, however, some drive shafts have one or both ends which are of smaller diameter than the remainder of the shaft. A smaller diameter end for a drive shaft has certain advantages, such as enabling the use of smaller universal joints than otherwise would be possible, as well as minimizing the space and weight of the parts required to couple the shaft to the universal joints.
It has been common heretofore simply to slide a substantially cylindrical liner into a hollow drive shaft from one end thereof, the liner being made of materials which damp vibrations and attenuate noise. Typical examples of such liners are disclosed in U.S. Pat. Nos. 2,751,765; 3,075,406; 4,014,184; and 4,909,361.
Liners of the kind in use heretofore cannot be used with propeller shafts that have a larger diameter between its ends than at the ends for the reason that the liner must be pushed into the shaft through the smaller diameter end and, consequently, must be of smaller diameter than that of the shaft between its ends. A liner having a diameter less than that of the shaft in which it is accommodated cannot damp vibrations, but instead will contribute to vibrations because the liner inevitably will be relatively movable within the larger diameter portion of the shaft.
Ideally, once a vibration damping liner is accommodated in a shaft the liner will be immovable relative to the shaft. Such an arrangement makes it possible to balance the shaft with the liner in place, and the balance of the shaft will not be adversely affected as the result of subsequent shifting of the liner within the shaft.
The ability of a liner to remain fixed in place within a shaft depends on a number of factors. For example, the liner should be formed of material which is sufficiently springy to enable the liner to bear forcibly against the surface of the bore of the shaft and thereby minimize the possibility of slippage occurring between the liner and the shaft. However, the inside and outside diameters of shafts and liners, respectively, are formed to dimensions having some tolerances, as a consequence of which not all of the shafts and liners have uniform diameter dimensions. It is necessary, therefore, to ensure that the outer diameter of the liner is sufficiently greater than that of the inner diameter of the shaft so that a radially expansive force constantly is exerted by the liner on the shaft. However, liners may be manufactured and stored for a considerable period of time prior to their assembly with shafts. If the material from which the liners are made is hygroscopic, ambient humidity will have an effect on the springiness of such material, thereby affecting the ability of the liner to exert a binding force on the shaft.
All of the foregoing problems exist in those instances in which a liner must be pushed through a relatively small diameter end of a shaft for accommodation in a larger diameter portion of such shaft. The necessity of the liner's having to pass through a relatively small diameter simply adds to the complexity of the liner's ability to damp vibrations.
An object of the invention is to provide a liner for accommodation in a cylindrical shaft and which not only has superior vibration damping characteristics so as to be usable in shafts of uniform diameter, but which also is adapted to be used with a cylindrical shaft whose diameter is not uniform.